1. Field of the Invention
The present invention relates to a deflection unit for mounting on a color cathode ray tube and is, in particular, concerned with positioning and adjusting the vertical coil in such a deflection unit.
2. Description of the Related Art
Deflection units are mounted on a cathode ray tube to deflect the electron beams across the screen in X- and Y-direction. The deflection unit consists essentially of two pairs of coils and a ferrite core which serves to return the magnetic flux. The one pair of coils produces a magnetic field which deflects the electron beams in horizontal direction (X-direction) while the other pair of coils serves vertical deflection (Y-direction).
During mounting of such a deflection unit the auxiliary vertical coil is first finished by winding a coil wire onto a prefabricated coil body and is then installed in the deflection unit. Tolerances of the components create deviations in the positions of the vertical coil, which might result in convergence and geometry errors. Therefore, after the vertical coil has been positioned, an adjusting operation is required for obtaining an optimum picture quality.
However, the adjustments known in the prior art are either too inaccurate or require complex devices which make the manufacture of such a deflection unit expensive.
It is therefore the object of the present invention to provide a deflection unit for mounting on a color cathode ray tube which permits an easier positioning and adjustment of the vertical coil. Furthermore a corresponding color cathode ray tube and an associated display apparatus shall be provided.
According to the invention this object is achieved by a deflection unit for mounting on a color cathode ray tube which comprises a coil body for a vertical deflection coil and first and second means for displacing the coil body in a first and second direction. The first and second directions are offset by about 90xc2x0 and are substantially positioned in parallel with the screen plane of the color cathode ray tube.
The invention permits a separate adjustment of the position of the vertical coil in X- and Y-direction in an advantageous manner.
Moreover, the deflection unit of the invention has a compact constructional shape so that it can easily be mounted on the neck of a color cathode ray tube.
In a preferred development of the invention each of the first and second means comprises a guided displacement bow member which can be displaced by means of a screw. Thanks to the constructionally identical design of the screws the manufacture of the deflection unit is further simplified.
When the vertical deflection coil is inserted into a cap of the deflection unit until it reaches a stop and when it is then rotated for fixing purposes, the positioning of the vertical coil relative to the Z-direction can be further simplified with respect to its manufacture.
Preferred developments of the invention are indicated in the subclaims.